As one example of an “interface,” a virtual private network (VPN) is a computer network that is implemented in an additional software layer (overlay) on top of an existing larger network for the purpose of creating a private scope of computer communications or providing a secure extension of a private network into an insecure network such as the Internet. The links between nodes of a virtual private network are formed over logical connections or virtual circuits between hosts of the larger network. The Network Layer protocols of the virtual network are said to be “tunneled” through the underlying transport network.
One common application of a VPN is to secure communications through the public Internet, but a VPN does not necessarily need to have explicit security features such as authentication or traffic encryption. For example, VPNs can be used to separate the traffic of different users or user communities over an underlying network.
While the use of VPNs is quite popular, other interfaces are also available to users including, but not limited to, Local Area Networks (LANs) or cellular telecommunications channels. Some of these interfaces operate independently of each other or in combination with one another. For example, a VPN could be established over a cellular channel.